Some machines include rotating shafts that are supported by bearing assemblies. For example, turbo machines such as gas turbine engines can operate by axial flow of a working fluid along a rotating shaft. The rotating shafts may be subjected to axial thrust forces exerted by the working fluid in opposite directions. The rotating shaft typically includes one or more runners or thrust plates extending therefrom that exert axial force against a thrust bearing assembly to maintain the axial position of the rotating shaft when exposed to the bi-directional thrust forces. Typical thrust bearing assemblies include two identical or at least similar types of thrust bearings that bear against opposite faces of the one or more runners. The thrust bearings are configured to absorb the full thrust forces in both directions to maintain the axial position of the rotating shaft.
The thrust bearings in typical thrust bearing assemblies can be relatively complex, including specially manufactured and assembled structures. Some thrust bearing assemblies utilize oil for lubrication between the thrust bearings and the runners. The oil may be relatively messy and may risk leakage from the thrust bearing assembly. Other thrust bearing assemblies are configured to utilize gas for lubrication by pumping a gas such as air through the thrust bearings and/or by specially-forming the thrust bearings to control gas flow. Additionally, the thrust bearing assemblies may be configured such that the runners mechanically engage the thrust bearings under certain conditions, such as during start-up and shut-down of the machine while the shaft rotates at speeds less than a designated operating speed. Some known thrust bearings and/or runners of the shafts are treated to include low friction coatings to reduce the frictional effects on the contacting surfaces and extend the lifetime of the thrust bearings. Due to the designs and features described above, typical thrust bearing assemblies may be relatively costly to produce and maintain.